Apparatus for treating iron ores preparatory to magnetic separation.



T. S. MAFFHT. APPARATUS FOR TREATING IRoN ORES PREPARATORY T0 MAGNETIC SEPARATION.

. APPLICAT ON FILED JULY 9,1914. 1,295,780.

Patented Feb. 25, 1919.

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' APPLICATION FILED JULY II 194. 1,295,780.

Patented 2 SHEETS- mm H I m i u, a I I a null-WW5!!! I! in I e r l 1 v5 45541354531. a r u. 00 0 I I I I UIIv T NII w v LE 44/ m I ww 71 UNITED STATES PATENT OFFICE.

THOMAS S. MAFFITT, OF ST. LOUIS, MISSOURI, ASSIGN OR, BY MESNE ASSIGNMENTS, TO

MISSISSIPPI VALLEY IRON COMPANY, OF WILMINGTON, DELAWARE, A CORPORA- TION OF DELAWARE.

APPARATUS FOR TREATING IRON ORES PREPARATORY TO MAGNETIC SEPARATION.

Specification of Letters Patent.

Patented Feb. 25, 1919.

Original application filed May 9, 1910, Serial No. 560,329. Divided and this-application filed July 9, 1914. Serial lilo 850,002.

To all whom it may concern:

Be it known that I, THOMAS S. MAFFn'r, a citizen of the United States, residing at St. Louis, State of Missouri, have invented certain new and useful Improvements in Apparatus for Treating Iron Ores Preparatory to Magnetic Separation, of which the following is a specification.

It has been previously proposed to render non-magnetic iron ores magnetic by subjecting the same to a reducing agent as a hydrocarbon as, but the treated ore has always been reduced to ordinary outside temperature before it. was passed through a magnetic separator.

I have discovered that by subjecting the ore to magnetic separation while hot at a temperature considerably above normal, ores can be separated which cannot be separated at all by the process outlined above. 7

The process generally stated consists in renderin the ore magnetic by heat treatment arid separating the ore from the gangue magnetically while in a heated state.

More specifically stated the process consists in heating the ore, subjecting the same to a reducing agent, preferably a hydrocarbon, and passing the treated ore in a heated state through a magnetic separator.

In order to describe the process and the apparatus for performing the same in detail reference is had to the accompanying drawings, in which:

Figure 1 is an elevation showing the apparatus;

Fig. 2 is a longitudinal section of the reducer; and

Figs; 3 and 4 are enlarged detail sectional views of the reducer.

The apparatus generally stated consists of a calciner A, a reducer B, and a magnetic separator C. While these separate parts of the entire apparatus may be of varied construction, an illustrative form of each will be described.

The calciner consists of a long rotary drum which is supported upon rolls 10 and is driven by means of intermeshing gears driven from a pulley 11. The drum extends vided with a heat resisting lining but is bare,

into an end casing 12 provided with a charging hopper 13 and into an end casing 14 provided with a discharge chute 15. A suitable pipe 16 extends into the head 14 and terminates in a burner whereby heat may be supplied to the interior of the drum. The end casing 12 has connected thereto a fan 17 'by means of which a current of air may be are lined with a heat resisting lining and have longitudinal ribs24 and 25 formed thereon. The upper end of the drum extends into a stationary portion 26 which has mounted thereon a filling hopper 26 and is provided with a hinged gate or closure 27. The lower end of the drum extends into an end portion 32 which is provided with a discharge chute 28 closed by a hinged gate or closure 29.

A device 30 for feeding a suitable reducing agent to the apparatus extends longitudinally thereof and comprises an outside pipe 31 suitably supported in the end 32 and in spiders 33. j A pipe 34'is located inside of the pipe 31 and is of smaller diameter so as to leave afree space between them. A third pipe 35 is located inside of the pipe 34 and is of smaller diameter so as to leave a free space between the pipes 34 and 35. In order to separate the different pipes a series of spacing blocks a are provided. The intermediate pipe 34 is open. at its end but the outside pipe 31 is closed and the pipe 35 extends through the closed end 36 and forms a tight joint therewith. The pipe 35 is connected to a suitable reservoir containing a reducing agent as crude oil or any other hydrocarbon compound. The pipes 31 and 34 form together a water jacket for the feed pipe 35, the water being admitted at 37 and discharged through pipe 38.

The lower end 40 of the drum is not proand a spray pipe 41 is arranged to direct a the same. The water spray is caught by a pan l2 arranged underneath the drum.

The magnetic separator C may be of any suitable construction. In this case it is of the Wenstrom type. v

The ore is admitted to the hopper 13 and passed through the drum A and is there sub- .jected to a heat treatment by means of the hot blast passing throughthe drum. The

ore as it leaves the drum in a highly heated state is discharged into the hopper 26- and the drum of the reducer B. As the ore passes through the reducer drum the reducing agent, which in this case is crude oil, is admitted through the pipe 35 and as it drops on the heated ore is converted into a gas. It will benoted that the end of the drum is of larger diameter than the end 21. The upper end of the cylinder is of large diameter so as to furnish a large volume for the hydrocarbon gases to act on the material. The lower end of the cylinder, or rather the lower half, is reduced in diameter so as to form a small outlet, thereby preventing entrance of air. As the ore is tumbled around inthe drum all parts of the ore will be thoroughly subjected to the generated gas and Will thus be rendered magnetic. As this ore reaches the lower end 40 of the drum it is cooled to some extent by the spray of water from the pipe 41. The ore in a heated state is discharged directly into the hopper 43 of the magnetic separator C and is then separated from its gangue. During the reducing operation the free access of air to the interior of the reducer apparatus must be prevented and it is for this purpose that the hinged valves or gates 27 and 29 are provided. These valves allow free admission and discharge of the ore but at the same time prevent free access of air.

The ore as it leaves the calciner will be highly heated, frequently as high as. 2000 F., and the ore as discharged from the reducer will still be at a comparatively high I temperature. The temperature at which the ore must be separated will vary somewhat,

, but I have found that for calcined brown hematite containing originally large percentages of clay gangue that the ore begins to lose its susceptibility to a magnetic field at 450 F. and below that temperature loses it very quickly, so that at ordinary temperatures it is practically non-magnetic. How- 'everif the temperature is kept above the critical point, which seems to be 450 F. for calcined brown hematite, the ore is found to be magnetic so that it can be separated by a magnetic separator without trouble.

The theory upon which the operation of this invention depends cannot be stated with definiteness. The ore as it leaves the calciner analyzes Fe O but the ore upon leaving the reducing kiln contains a distinct amount of F e 0 and Fe O- However if the ore When it leaves the reducer is allowed to cool too much it loses its magnetism, but even after it loses its magnetism it still analyzes the same as before. This result leads to the conclusion that the change isof a physical nature rather than of a chemical nature. Furthermore, in breaking open a large lump, for instance a lump two inches in diameter, it is found that the interior as you go toward the inside is less magnetic than the outside. It is also found that the magnetism penetrates deeper into porous ore than into dense ore. This result leads to the conclusion that the action which takes place in the reducing apparatus forms what might be termed a magnetic film on the exteriorof the ore suflicient to make it susceptible to a magnet while the ore is still hot. I do not however desire to be understood as advancing this theory as the only one or as being necessary, but merely one which maybe advanced from the results obtained. The results show that when the iron ore is rendered magnetic by the process described and maintained above the critical temperature, which for calcined brown hematite clayey ores is 450 F., it can be 'efliciently separated magnetically while when the temperature drops below the critical point the ore is practically non-magnetic.-

It is to be understood that the ore is cooled down in the section40 so as to prevent injury to the magnetic separator. It seems however that the permeability increases with the temperature so that it is desirable to maintain ashigh a temperature as possible.

The above described apparatus may be varied to suit requirements, for instance, the rotary drum A may be replaced by another form of calcining kiln, and other types of reducers may be .provided. The term reducer is here used to designate an apparatus for reducing the iron from a non-magnetic to a magnetic state. Generally this is accomplished by a reducing gas] This process is especially useful and convenient when used in connection with the process described in the above mentioned patent of Edward F. Goltra. In the'above application the clay iron ore is passed through the drum and heated by the hot blast, tumbled and agitated so as to shake loose the gangue from the ore, and subjected rendered magnetic and then can be easily separated from the clay balls or from the remaining clay by means of the magnetic separator.

Instead of utilizing the reducer and the magnetic separator for separating the clay balls from the ore, it is possible to perform this step of the process in other Ways, for instance by means of suitable jigs. A suitable ap aratus for this purpose is the well known radfordjig. In both ofthe methods enumerated however, the ore is prepared in the previous step for operation in the succeeding step of the process.

No claim is herein made to the process described which latter forms the subject matter of a separate application, viz. Serial No. 560,329, filed May 9, 1910 of Which th-is application is a division. I

It is obvious that various changes may be made Without departing from the spirit of this invention and it is therefore to be understood that this invention is not to be limited to the specific arrangements or'construction shownand described:

Having thus described the invention! What is claimed as new is:

1. In an apparatus for treating ores preparatory to magnetic separation, a drum having admission and discharge openings and adapted to pass the ore therethroug'h,

the cross section-of said drum being greater at the ore admission end than at the ore discharge end, and means for maintaining an atmosphere in said drum adapted to render the ore magnetic.

2. In an apparatus for treating ores preparatory to magnetlc separation, adrum comprising a section of comparatively large diameter provided with an ore admission opening and a section of comparatively small diameter provided with a discharge opening, means for supporting said drum for rotation adapted to pass ore therethrough, and

means -f0r maintaining an atmosphere in said drum adapted to render the ore magnetlc.

-3, In an apparatus for treating ores preparatory to magnetic separation, a drum havlng admission and discharge openlngs and adapted to pass the ore therethrough,

the, cross section of said drum being greater at the admission end than at the discharge end, means for maintaining an atmosphere in said drum adapted to render the oremagnetic, and ore inletand outlet closures for said drum adapted toseal said drum.

4. In an apparatus for'treating ores preparatory. to magnetic separation, a drum having admission and discharge'openings and. adapted to pass the ore therethrough,

the cross section ofsaid drum being greater adapted to permit the ore to pass there through, means for rotating said drum, and a pipe extending along said drum and adapted to discharge a reagent on the ore to become vaporized thereby so as to create in said drum an atmosphere adapted to render the ore magnetic.

6. In an apparatus for treating ores preparatory to magnetic separation, an inclined drum having an inlet and an outlet and adapted to permit the ore to pass therethrough, means for rotating said drum, and a jacketed pipe extending along said drum and adapted to discharge a reagent on the ore to become vaporized thereby so as to create in said drum an atmosphere adapted to render the ore magnetic.

' .In testimony whereof I aflix my signature in presence of two witnesses.

THOMAS S.-MAFFITT.

Wit'nessesi EDWARD F. GoL'rRA, J. D. DANA. 

